Caption: False-colour shadow transmission electron micrograph (TEM) of the rod-shaped, Gram- negative bacterium, Escherichia coli, commonly known as E. coli. Part of the normal fauna of the gut in humans & animals, E. coli may give rise to infection under certain conditions. Serotypes of E. coli are responsible for gastro-enteritis in children, particularly in tropical countries. In adults it is the cause of "traveller's diarrhoea", and the majority of urinary tract infections. It is also the organism most used in genetic engineering studies. Magnification: x6800 at 6x7cm size.